Robotic surgical systems have been used in minimally invasive medical procedures. During such a medical procedure, the robotic surgical system is controlled by a surgeon interfacing with a user interface. The user interface allows the surgeon to manipulate an end effector that acts on a patient. The user interface includes an input controller or handle that is moveable by the surgeon to control the robotic surgical system.
The end effectors of the robotic surgical system are positioned at the end of robotic arms. Each end effector is manipulated by an instrument drive unit (IDU). The IDU includes a drive motor that is associated with the end effector to move the end effector about a respective axis or to perform a particular function of the end effector (e.g., approximate, pivot, etc. jaws of the end effector). The IDU can include a plurality of drive motors with each drive motor being associated with a respective degree of freedom or function of the end effector.
Each drive motor of the IDU can be associated with the respective degree or degrees of freedom of the end effector by a drive mechanism (e.g., a drive cable, a drive rod and/or a drive screw). To precisely control the end effector about the degree(s) of freedom the respective drive mechanism can be pretensioned.
There is a continuing need to pretension and limit forces experienced by the drive cables. In addition, there is a continuing need for precisely and accurately measuring the force applied by the drive motors in order to anticipate and predict a life expectancy of the drive motors and drive mechanisms.